Blood pumps include intracorporeal embedded type pumps, so-called artificial hearts, and pumps for extracorporeal use. One requirement associated with both types of blood pumps is that they not generate hemolyzation or thrombus. In addition, the former type of blood pump is required to meet especially high technical demands because they are difficult to replace.
In recent years, attention has been directed at developing a continuous flow pump, for use as a blood pump, that is capable of being easily reduced in size. In the continuous flow type pumps, a magnetic bearing or hydrodynamic bearing, in which an impeller and a blood chamber do not make contact in the pump, is often used in order to restrain the generation of hemolyzation or thrombus.
In the case of both the magnetic bearing and the hydrodynamic bearing, the impeller for feeding blood is levitated in the blood chamber, by use of an attractive force (or repulsive force) of a permanent magnet and a force balancing therewith. The attractive force (or repulsive force) of an electromagnet is used as the balancing force in the case of the magnetic bearing, and a force generated by hydrodynamic grooves is used as the balancing force in the case of the hydrodynamic bearing.
A magnetic bearing pump has been proposed in Japanese Patent Laid-open No. 2002-303288. This centrifugal type liquid pump device 1 includes: a pump section 2 having an impeller 21 rotated inside a housing 20; an impeller rotating torque generating section 3 including a rotor 31 having magnets 33 for attracting the impeller 21, and a motor 34 for rotating the rotor 31; a pump device body section 5 having an impeller position control section 4 including electromagnets 41 for attracting the impeller 21; and a control unit 6.
The present applicant has proposed a hydrodynamic bearing pump in Japanese Patent Laid-open No. 2003-201992(corresponding to U.S. Pat. No. 6,840,735). This centrifugal type liquid pump device 1 includes: a pump section 2 having an impeller 21 rotated inside a housing 20; a body section 5 including a rotor 31 having impeller attracting magnets 33, a motor 34 for rotating the rotor 31, electromagnets 41 for attracting the impeller 21, an impeller position detecting sensor 42, and hydrodynamic grooves 38 formed in the inside surface of the housing 20; and a control mechanism 6.
For more information, refer to Japanese Patent Laid-open Nos. 2003-210572(corresponding to U.S. Pat. No. 7,033,147), 2005-270345(corresponding to U.S. Patent Application Publication No. 2005/287022), and 2005-287598 (corresponding to U.S. Patent Application Publication No. 2005/287022).